February is the second and shortest month of the year in the Julian and Gregorian calendar with 28 days in common years and 29 days in leap years, with the quadrennial 29th day being called the leap day. It is the first of five months to have a length of fewer than 31 days (the other four months that fall under this category are: April, June, September, and November), and the only month to have a length of fewer than 30 days, with the other seven months having 31 days. In 2019, February had 28 days.

The Roman month Februarius was named after the Latin term februum, which means purification, via the purification ritual Februa held on February 15 (full moon) in the old lunar Roman calendar. January and February were the last two months to be added to the Roman calendar, since the Romans originally considered winter a monthless period. They were added by Numa Pompilius about 713 BC. February remained the last month of the calendar year until the time of the decemvirs (c. 450 BC), when it became the second month. At certain intervals February was truncated to 23 or 24 days, and a 27-day intercalary month, Intercalaris, was inserted immediately after February to realign the year with the seasons.

Under the reforms that instituted the Julian calendar, Intercalaris was abolished, leap years occurred regularly every fourth year, and in leap years February gained a 29th day. Thereafter, it remained the second month of the calendar year, meaning the order that months are displayed (January, February, March, ..., December) within a year-at-a-glance calendar. Even during the Middle Ages, when the numbered Anno Domini year began on March 25 or December 25, the second month was February whenever all twelve months were displayed in order. The Gregorian calendar reforms made slight changes to the system for determining which years were leap years and thus contained a 29-day February.

Historical names for February include the Old English terms Solmonath (mud month) and Kale-monath (named for cabbage) as well as Charlemagne's designation Hornung. In Finnish, the month is called helmikuu, meaning "month of the pearl"; when snow melts on tree branches, it forms droplets, and as these freeze again, they are like pearls of ice. In Polish and Ukrainian, respectively, the month is called luty or лютий, meaning the month of ice or hard frost. In Macedonian the month is sechko (сечко), meaning month of cutting [wood]. In Czech, it is called únor, meaning month of submerging [of river ice].

In Slovene, February is traditionally called svečan, related to icicles or Candlemas.[2] This name originates from sičan,[3] written as svičan in the New Carniolan Almanac from 1775 and changed to its final form by Franc Metelko in his New Almanac from 1824. The name was also spelled sečan, meaning "the month of cutting down of trees".[2]

In 1848, a proposal was put forward in Kmetijske in rokodelske novice by the Slovene Society of Ljubljana to call this month talnik (related to ice melting), but it did not stick. The idea was proposed by a priest, Blaž Potočnik.[4] Another name of February in Slovene was vesnar, after the mythological character Vesna.[5]

Having only 28 days in common years, February is the only month of the year that can pass without a single full moon. Using Coordinated Universal Time as the basis for determining the date and time of a full moon, this last happened in 2018 and will next happen in 2037.[6][7] The same is true regarding a new moon: again using Coordinated Universal Time as the basis, this last happened in 2014 and will next happen in 2033.[8][9]

February is also the only month of the calendar that, once every six years and twice every 11 years consecutively, either back into the past or forward into the future, has four full 7-day weeks. In countries that start their week on a Monday, it occurs as part of a common year starting on Friday, in which February 1st is a Monday and the 28th is a Sunday; this occurred in 1965, 1971, 1982, 1993, 1999 and 2010, and occur will again in 2021. In countries that start their week on a Sunday, it occurs in a common year starting on Thursday, with the next occurrence in 2026, and previous occurrences in 1987, 1998, 2009 and 2015. The pattern is broken by a skipped leap year, but no leap year has been skipped since 1900 and no others will be skipped until 2100.

February meteor showers include the Alpha Centaurids (appearing in early February), the Beta Leonids, also known as the March Virginids (lasting from February 14 to April 25, peaking around March 20), the Delta Cancrids (appearing December 14 to February 14, peaking on January 17), the Omicron Centaurids (late January through February, peaking in mid-February), Theta Centaurids (January 23 – March 12, only visible in the southern hemisphere), Eta Virginids (February 24 and March 27, peaking around March 18), and Pi Virginids (February 13 and April 8, peaking between March 3 and March 9).

This list does not necessarily imply either official status or general observance. Please note that all Baha'i, Islamic, and Jewish observances begin at the sundown prior to the date listed, and end at sundown of the date in question unless otherwise noted.